Native South Americans Reached Polynesia Early

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News & views observations of weather during the first Smyth (eds Duffy, P. J. & Nolan, W.) Ch. 5 (Geography Polynesian DNA markers with those of people seven centuries bc, and which remain largely Publs, 2012). from other regions, including Europe, Amer- 7 4. Freeman, A. M. (ed.) Annála Connacht: The Annals of unexploited. As Pfister and Wanner stated in Connacht, A.D. 1224–1544 (Dublin Inst. Advanced Studies, ica, Africa and Melanesia. A computational 2002, “Worldwide, many thousand volumes 1944). method called an ADMIXTURE analysis with daily observations exist, but have not yet 5. Brooks, C. E. P. Q. J. R. Meteorol. Soc. 54, 309–317 (1928). allowed Ioannidis and colleagues to work out a 6. Chambers, F. M. & Brain, S. A. Holocene 12, 239–249 been analyzed for their climatic information. (2002). person’s probable genetic ancestry and ances- Let’s get to work!” 7. Pfister, C. & Wanner, H. Past Glob. Changes Mag. 10, 2 tral geographical origins through studies of (2002). gene flow. Their main discovery is that several 8. Brázdil, R., Pfister, C., Wanner, H., Von Storch, H. & Francis Ludlow and Rhonda McGovern Luterbacher, J. Clim. Change 70, 363–430 (2005). eastern Polynesian populations have signs of are at the Trinity Centre for Environmental 9. White, S., Pfister, C. & Mauelshagen, F. (eds) The Palgrave a background signature (genetic traces from Humanities, School of Histories and Handbook of Climate History (Palgrave Macmillan, 2018). distant ancestors) that originated from Native 10. Camenisch, C., Bauch, M., Huhtamaa, H., Pei, Q. & Humanities, Trinity College, Dublin D02 PN40, White, S. Past Glob. Changes Mag. 27, 73 (2019). South American people. Ireland. 11. Blöschl, G. et al. Nature 573, 108–111 (2019). How did Ioannidis and colleagues solve this 12. Gao, C., Ludlow, F., Amir, O. & Kostick, C. Quat. Int. 394, e-mail: [email protected] 180–193 (2016). complex task of genetic unravelling? In their 13. Pfister, C. et al. Clim. Change 131, 191–198 (2015). admixture studies, they could trace and dis- 1. Blöschl, G. et al. Nature 583, 560–566 (2020). 14. Huijs, J., Pirngruber, R. & van Leeuwen, B. in A History tinguish between different modern colonial 2. Paprotny, D., Sebastian, A., Morales-Nápoles, O. & of Market Performance: From Ancient Babylonia to the Jonkman, S. N. Nature Commun. 9, 1985 (2018). Modern World (eds van der Spek, R. J., van Leeuwen, B. & admixtures; for example, in French Polynesia, 3. Ludlow, F. in At the Anvil: Essays in Honour of William J. van Zanden, J. L.) 128–148 (Routledge, 2015). there was a large French influence, whereas Spanish and Chilean groups were part of the population history in Rapa Nui. A key discovery Human migration came from their analysis of people from Rapa Nui — a signature could be assigned to Native Native South Americans South American populations from northern coastal regions of South America, and this component was independent of other large reached Polynesia early historical, or more-recent, admixture events. This signature exists in the genetic background, indicating that it is an old and stable Paul Wallin hallmark of admixture. A surprising finding DNA analysis of Polynesians and Native South Americans is that this signal was also identified in other has revealed an ancient genetic signature that resolves a eastern Polynesian populations, for example long-running debate over Polynesian origins and early contacts in populations in Mangareva, in North Marque- sas and South Marquesas, and in Palliser in the between the two populations. See p.572 Tuamotu Islands (Fig. 1). These other islands lie farther from South America than does Rapa Nui, although for people sailing from South For many years, scholars have speculated best-known example considered concerning America they are destinations that would be about how Polynesia was initially populated. such contacts4. It is a part of Polynesia that aided by favourable trade winds and currents. On page 572, Ioannidis et al.1 now describe a is located relatively close to South America, Ioannidis et al. investigated the estimated genetic approach that they used to address the and in Rapa Nui there is evidence of large, timing of admixture events using a method issue of Polynesian origins and interactions. ancient sweet-potato fields, extraordinary called tract-length distribution analysis, The early peopling of Polynesia attracted old stonework and a specific birdman cult — which assesses the length distributions of worldwide interest in 1947, when the all of which are features in common with those the genomic segments inherited from differ- Norwegian explorer Thor Heyerdahl set sail of South America. ent ancestral populations. As expected, this on the Kon-Tiki expedition to test his migration Ioannidis and colleagues analysed the DNA statistical approach suggests that the Euro- theory2. The crew left Peru on a wooden raft, pean admixtures in Polynesia first date back and after 101 days and a voyage of more than “Future research should to colonial phases of ad 1750–1860. 7,000 kilometres, they reached Polynesian The authors made the notable discovery shores, thus demonstrating the possibility assess the possibility of more that an initial admixture event between of early travel from South America to these than just one early contact Native South Americans and Polynesians took Pacific islands. Heyerdahl challenged the from South America.” place in eastern islands of Polynesia around scientific community’s view that evidence ad 1150–1230. Previous work3,5 is consistent pointed instead to the peopling of Polynesia by with a model of populations spreading east- people travelling east from Asia, and his idea of people from Rapa Nui, and also studied wards from Asia possibly having reached that Polynesia was initially populated by South DNA of individuals from 17 populations of eastern Polynesia by that time. The exception Americans was generally criticized by scholars. Pacific islands and 15 Native American popu- to this South American admixture timeframe The same scientific community nevertheless lations from the Pacific coast of South Amer- is Rapa Nui, which had a later admixture, dated discussed cultural contacts between the two ica. Genome-wide DNA analyses of 807 people to around ad 1380. This later date for Rapa Nui regions, because a South American plant, the (analysing predominantly present-day indi- is surprising, because it is the closest site to sweet potato, has a long history of cultivation viduals) enabled the authors to search for evi- South America studied and has been cited as in eastern Polynesia. The idea that Polynesians dence of ancestors from different populations the ‘typical’ example of a location with possible voyaged to South America and introduced who produced offspring together — thereby early connections to South America. However, the plant on their return to Polynesia generating a combined genetic signature of the timing difference might be due to a more became the accepted explanation for this3. the two populations, described as an admix- complex genetic history there because of Rapa Nui (also known as Easter Island) is the ture. The authors compared the dominant relatively recent Chilean genetic input.

When Ioannidis and colleagues searched for similarities between the genetic signatures of Native South Americans found in Polynesia South Pacific Ocean Marquesas and those of Indigenous populations in North admixture COLOMBIA northern coastal areas of South America, the Marquesas by AD 1150 Migration from connection to Colombian populations was Migration from Asia admixture to western Polynesia by AD 1200 Colombia especially strong. The earliest genetic signal (1500–800 BC) PERU of Native Southern Americans found by the authors in Polynesia was from people of the Migration to Palliser Rapa Nui Southern Marquesas islands, and the authors eastern Polynesia admixture (Easter Island) argue that Colombians mixed with Polynesians AUSTRALIA (by ~ AD 1025) by AD 1230 admixture there around ad 1150. This date is so early Mangareva by AD 1380 that it could even suggest South Americans admixture by AD 1230 reached there before Polynesians arrived, NEW ZEALAND which would make Heyerdahl partly right if it were the case that South Americans first settled at least the area of eastern Polynesia Figure 1 | Genetic clues reveal early migration from South America to Polynesia. Ioannidis et al.1 report that has signs of early admixture. a DNA analysis of Polynesians and Native American people from South America, focused mainly on modern The authors propose that the Native populations. The authors shed light on the early peopling of Polynesia by uncovering signs of ancient South American genetic signatures they encounters between Polynesians and South Americans (probably those from Colombia), which resulted in found were probably the result of a single a genetic signature called an admixture indicating that children had parents from both populations. The ancient contact. Their model suggests that earliest signs of such admixture in Polynesia were estimated to have occurred on the Southern Marquesas islands in ad 1150. Previous studies3,5 indicate that populations moving eastwards from Asia had populated the mixed population then spread from this area by around that time. The authors find evidence for the same type of population admixture being central eastern Polynesia around ad 1200 present between ad 1150 and ad 1230 in nearby islands, and then in Rapa Nui (also known as Easter Island) to other Polynesian islands during an early by ad 1380. Some Polynesian islands, including Rapa Nui, have characteristics in common with those of eastern Polynesian expansion, and finally ancient South America, such as elaborate stonework and the sweet-potato plant. But an early role for South reached Rapa Nui. These spectacular results Americans in the peopling of the Polynesian islands had not previously been widely accepted. have major implications for future discussions concerning early migrations and interactions in Polynesia. Rapa Nui itself is not suggested had a gene admixture event dated to around the mystery about a possible early Native to be the initial point of contact between ad 1380 — those arrivals therefore reached an South American physical presence in eastern Polynesians and South Americans, but the island that was probably already populated by Polynesia, and that is a great contribution. admixture identified there is thought to have other Polynesians. Radiocarbon dating evi- arisen elsewhere in Polynesia in a population dence5,7,8 places the initial settlement phase Paul Wallin is in the Department of that eventually reached Rapa Nui (Fig. 1). of Rapa Nui to at least ad 1200. However, the Archaeology and Ancient History, Uppsala The authors also raise other possible contact building phase of the elaborate monumen- University, Campus Gotland, Visby SE-621 67, scenarios: for example, that Polynesian tal stone structures there took place around Sweden. populations made voyages to South America ad 1300–1400, which is early compared with e-mail: [email protected] and then returned to Polynesia along with when similar such construction occurred in South American people, or that people the central region of eastern Polynesia9. If this returned to Polynesia who carried Native stonework is a result of cultural contacts, it South American genetic heritage. Ioannidis could imply that another independent connec- et al. suggest that further genetic studies tion with Native South Americans took place will be needed to address such alternative on Rapa Nui during that timeframe. This offers hypotheses. another explanation for why Rapa Nui had a What are the implications of the authors’ late timing for the estimated admixture date. results for future research? From an archae- Genetic studies of specimens of early ological viewpoint, the next step would be to sweet-potato plants in herbarium collections assess how well their model fits with materi- from the eighteenth century suggest that such al-culture studies, ethno-historical records, plants found in Polynesia originated from the 1. Ioannidis, A. G. et al. Nature 583, 572–577 (2020). linguistics and evidence of plant and animal northern coasts of South America, and some 2. Heyerdahl, T. American Indians in the Pacific: The Theory distributions. Linguistic research6 has led genetic variations found in the specimens Behind the Kon-Tiki Expedition (Allen & Unwin, 1952). 3. Kirch, P. V. On the Road of the Winds: An Archaeological to the proposal that a general, intermixed indicate the possibility of several introduc- History of the Pacific Islands Before European Contact central eastern Polynesian language group tion events in Polynesia10. Future research 2nd edn (Univ. California Press, 2017). 4. Green, R. in Easter Island and East Polynesian Prehistory developed owing to interactions between dif- should assess the possibility of more than (ed. Vargas Casanova, P.) 87–110 (Univ. Chile Press, 1998). ferent populations. That study suggested that just one early contact from South America, as 5. Wilmshurst, J. M., Hunt, T. L., Lipo, C. P. & Anderson, A. J. Rapa Nui was not included as part of this net- well as considering long-reaching interaction Proc. Natl Acad. Sci. USA 108, 1815–1820 (2011). 11 6. Walworth, M. Oceanic Linguist. 53, 256–272 (2014). work, but that the language used in Rapa Nui networks and voyaging between islands , 7. Martinsson-Wallin, H. & Crockford, S. J. Asian Perspect. instead split directly from an early language possibly also including Rapa Nui. 40, 244–278 (2002). group termed Proto-Eastern Polynesian6. This DNA studies will be necessary to answer 8. Mulrooney, M. A. J. Archaeol. Sci. 40, 4377–4399 (2013). 9. Martinsson-Wallin, H., Wallin, P., Anderson, A. & Solsvik, R. suggests that the first inhabitants to reach some of the remaining questions, and should J. Island Coast. Archaeol. 8, 405–421 (2013). Rapa Nui arrived there quite early. analyse living populations not included in the 10. Roullier, C., Benoit, L., McKey, D. B. & Lebot, V. Proc. Natl It is worth reflecting that, for the model in authors’ study, as well as DNA extracted from Acad. Sci. USA 110, 2205–2210 (2013). 11. Olivares, G. et al. PLoS ONE 14, e0217107 (2019). which the people settling on Rapa Nui who ancient bones. Nevertheless, Ioannidis and were from elsewhere in eastern Polynesia and colleagues’ core findings have finally solved This article was published online on 8 July 2020.